Near-eye displays may be broadly categorized into two types: virtual reality displays and augmented reality displays. A virtual reality near-eye system may include a wearable device (e.g., a head-mounted display) that includes display optics, such as lenses, that are opaque to ambient light from the environment. Certain virtual reality near-eye systems may include two displays (e.g., one for each eye of a user) that project respective computer-generated images that are sized and focused for viewing by both eyes of the user. Other virtual reality near-eye systems may include a single display that projects a single computer-generated image that is visible to both eyes.
An augmented reality near-eye system may include a wearable device with display optics that are substantially transparent to ambient light. Such display optics may include, for example, narrow-band reflectors, partial reflectors, holographic reflectors, or other display optics that operate to redirect projected light into a user's eye while permitting a substantial portion of ambient light to pass through as well. This produces the effect of having the projected image appear as an overlay on a real-world environment.